fully controlled bridge

[Springles]

Hi:
I need some help. I gonna control the speed of DC motor, so I gonna use a single-phase fully controlled bridge rectifier. I have a NI USB-6008, with it a goona make the pulses to the scr's; so I need to know how can I synchronize this pulses with the frecuency of the source??, and how can I move this pulses to vary the speed?.

Thank you

[Pnt]

Is the "source" the mains 230 or 110 AC voltage ?

Why don't you apply the pulses after the bridge?

You need to tell us more , for your project.

[Pnt]

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I wrote:

Why don't you apply the pulses after the bridge?

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Of course you do that... typing without thinking...

I don't know  NI USB-6008 but i guess you can measure analog voltage. So you can find the zero cross point...

[Springles]

Hi:
The source is 230 AC, I need to control the pulses for the SCR´s, with the NI USB-6008 a can measure analog voltage so I can find the zero cross, and with it a can make the pulses, but I don´t know with wich function can I synchronise my pulse train with the source because I want to control this pulses to fired my scr´s in different parts of the sine wave of the source.

[Pnt]

If you can find the zero cross, you can synchronize your pulses, wherever you want as the frequency is stable, 50 Hz (or 60Hz).

You just measure time inside one half-period. Then another zero cross will occur, and you restart measuring time.

The only thing i am not sure, is that you probably need a real-time software to do that. If you rely on windows... you will have problems, for sure...

Message Edited by Pnt on 05-05-2008 08:17 AM